1. Field of the Invention
The present invention relates to a surge absorber which is used for preventing an accident by protecting a variety of apparatuses from an abnormal voltage (surge voltage). The surge absorber is, for example, used as a lightning surge voltage or an electrostatic countermeasure for a variety of electronic apparatuses or a variety of apparatuses including electronic apparatuses.
Priority is claimed on Japanese Patent Application No. 2006-89955, filed on Mar. 29, 2006, Japanese Patent Application No. 2006-336882, filed on Dec. 14, 2006 and Japanese Patent Application No. 2006-356115, filed on Dec. 28, 2006 at the Japanese Patent Office, the disclosure of which is incorporated herein by reference.
2. Description of Related Art
A surge absorber is connected to a portion which is apt to be subjected to electric shock caused by lightning surge voltage or electrostatic surge voltage and the like, such as a portion in which an electronic apparatus for a communication apparatus such as a telephone, a facsimile machine or a modem device is connected to a communication line, a portion in which an electronic apparatus is connected to a power supply line, an antenna or a CRT driving circuit, in order to prevent damage due to heat or ignition of the electronic apparatus or a printed board having the electronic apparatus mounted thereon caused by abnormal voltage.
Recently, with the high-density mounting of electronic apparatuses, small-sized surface-mounted components are in demand even in a discharge type surge absorber for a communication line or a power supply line. In order to satisfy such demands, a surge absorber in which a pair of sealing electrodes is formed with a convex shape and can be surface-mounted with a small size is suggested (for example, see Japanese Unexamined Patent Application Publication No. 2005-63721).
In such a surge absorber, the distance between the electrodes needs to be adjusted in order to adjust the discharge starting voltage without changing an electrode material, sealing gas and a sealing gas pressure.
However, in the surge absorber disclosed in the above-described Publication, the length of the discharge electrode needs to be changed in order to change the distance between the electrodes and thus high manufacturing cost such as high manufacturing cost of a mold is incurred.
Conventionally, this type of a surge absorber includes a pair of discharge electrodes which is provided at a predetermined discharge gap in a sealing container having a predetermined dimension (Japanese Unexamined Patent Application Publication No. Hei 6-132065).
FIG. 15 shows an example of a conventional surge absorber. In this surge absorber S, a pair of lead wires 301a and 301b is provided at a predetermined gap and penetrate through a base 300 formed of an insulating material in an airtight manner. Discharge electrodes 302a and 302b formed of iron (Fe), nickel (Ni), copper (Cu) or an alloy thereof are provided in a parallel manner on one end of the pair of lead wires 301a and 301b and an airtight container 303 formed of the insulating material such as glass is provided on the base 300 to surround the discharge electrodes 302a and 302b. Discharge gas including inert gas such as argon (Ar) or nitrogen (N) gas is filled in the airtight container 303.
In the surge absorber S having the above-described configuration, the lead wires 301a and 301b are connected between the lines of protected apparatuses, for example, the lines of electronic apparatuses. When a surge is applied to the lines, an aerial discharge is generated between the discharge electrodes 302a and 302b and the surge is absorbed therebetween such that the electronic apparatus is protected from the surge.
However, in the surge absorber S, it is difficult to obtain a stable discharge starting voltage. In addition, when a powerful surge is applied, the discharge starting voltage increases and thus the function of the surge absorber may not be sufficiently accomplished.